Reaction motor with fluid cooling means



Aug. 29, 1950 zuc ow 2,520,751

REACTION "OTOR WITH FLUID COOLING MEANS Filed Feb. 19, 1944 2 sheets sheet 1 E INVENTOR. G NA UE/CE cl. Zuc/eow CM, -J

A TTORNE Aug. 29, 1950 M. J. ZUCROW REACTION MOTOR wrru FLUID COOLING MEANS 2 Sheets-Sheet 2 Filed Feb. 19, 1944 INVENTOR. MAURICE J Zucwow A TTOENEX Patented Aug. 29, 1950 2,520,751 REACTION MOTOR WITH FLUID COOLING MEANS Maurice J. Zucrow, Altadena, CaliL, assignor to Aerojet Engineering Corporation, Azusa, Calii'., a corporation of Delaware Application February 19, 1944, Serial No. 523,169

4 Claims. 1

This invention relates to thrust motors of the jet opera-ted type and has for its objects to provide an arrangement for feeding liquid to be injected into the motor and to protect the device from damage due to thermal distortion.

Thrust motors of the jet propulsion type are known in the art. They ordinarily comprise a combustion chamber with an exhaust nozzle leading from the chamber to the exterior, the fuel being burned at a rapid rate in the chamber and the gases resulting from the combustion being ejected at high velocity through the nozzle. High degrees of heat are generated in the chamber and the exhaust nozzle. It is desired to maintain the motor wall temperature in contact with the hot gases, below the dangerous level.

In accordance with my invention I provide a cooling jacket around the nozzle of the chamber and cause either the liquid fuel or liquid oxidizer to flow through it prior to its injection into the motor. In such an arrangement there is danger of destruction or damage to the inner wall of the'motor in contact with the hot gases due to the fact that this part of the motor and nozzle expand by heating differently than does the jacket wall which surrounds it. In accordance with my invention I incorporate into the walls of the jacket a flexible-device adapted to expand or contract with the differential expansion between v the inner wall and the jacket.

Features of the invention reside in the arrangement and organization of the expansible member.

According to another feature I provide liquid cooling where the heat is generated and particularly at the exhaust nozzle. A related feature resides in a construction of the cooling fluid passageway so that the most rapid fluid flow occurs over the region where the greatest rate of heat transfer takes place.

The invention will be better understood from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings in which:

Fig. 1 is a cross sectional elevation of a jet thrust motor having an expansion joint in accordance with this invention;

Fig. '2 is a cross sectional elevation of a jet thrust motor in which the expansion joint is associated with the injector nozzle;

Fig. 3 is a cross sectional elevation of a jet thrust motor having a modified form of an expansion joint according to this invention;

Fig. 4 is a partial cross sectional elevation of a jet thrust motor having another modified form of an expansion joint according to this invention;

Fig. 5 is an end view thereof; and

Fig. 6 is a cross section taken at line 6-6 of Fig. 4.

2 Similar numerals refer to similar parts throughout all the figures in the drawing.

Fig. 1 shows a jet motor comprising a, combustion chamber formed by a. cylindrical wall I and shaped at one end to form the usual exhaust jet opening at la. The head of the combustion chamber is closed by a plate 6. A chamber B is formed by a cup-shaped member 9 which is attached around the periphery of plate 6. A fuel pipe l2 leads into combustion chamber A by passing through chamber B without communicating with it, but communicating with a hole 14 in plate 6. The pipe I2 passes through a conventional packing nut ll holding packing Ha against the pipe to prevent leakage of liquid from chamber B. Plate 6 is provided with a number of openings 8 through which liquid from chamber B may be injected into combustion chamber A.

The combustion chamber and exhaust nozzle are surrounded by a jacket 2, shown cylindrical in form and attached at one end to plate 6 and at the other end to an annular ring 3 fastened to the exhaust .end of the nozzle. The jacket 2 provides a chamber C around the combustion chamber and nozzle, which may be filled with a liquid as shown, and this liquid is adapted to pass into chamber B through an opening I in. plate 6. When injection holes 8 are provided in plate 6 the liquid in chambers -B andC should be one which is used in the operation of the motor. The liquid in the jacket serves to coolv the motor and thereby improve its operation.

Inasmuch as the temperature of the wall I will be much higher than the temperature of the outer jacket 2, which may likely be of a different material than the jacket, there tends to occur an unequal thermal expansion of the jacket and the wall I which would tend to distort the inner wall I and perhaps injure the motor. To avoid this difficulty I provide as part of the jacket wall 2 a flexible member 5 in the form of a bellows as shown. This member 5 is of a material which can bend without cracking so that when wall 2 expands or contracts the wrinkles in the member will correspondingly move together or apart to take up the expansion or the contraction. The flexible member may be made integral and of the same material as the jacket 2.

The flexible member is located away from the exhaust nozzle la and adjacent to the combustion chamber. This position of the bellows has the advantage that the flexible member itself is not likely to be subjected to excessive thermal expansion as would be the case if it were placed in the region of greatest rate of heat transfer next to the nozzle. It will accordingly operate with less thermal expansion in itself than occurs in jacket 2 adjacent the nozzle, and this serves to facilitate the flexible or elastic operation.

In operation, fuel may be injected into chamber A through pipe I2 under suflicient pressure to overcome the pressure of the chamber and simultaneously the liquid in chamber C, ordinarily an oxidizing agent for the fuel, is injected into the chamber through holes I which are placed at such an angle to meet the stream of fuel from opening I4. The oxidizer will beiniected under pressure from a pressure source attached to the filler pipe 4. The combustion of fuel produces high temperature gases whose velocity increases to supersonic values as they flow through the nozzle. The heat flow intensity to the coolant is greater at the region of high velocity than it is in the combustion chamber where the velocity is lower. The liquid in chamber will conduct away the heat from the jet nozzle to the outer jacket 2,'causing its temperature to rise. Since the temperature of the jacket 2 is less than that of wall In there will be unequal expansion of the walls I and In and the wall 2 and this difierence will be taken up by the flexible member 5.

Fig. 2 shows another modification of a jet thrust motor having a cooling jacket of which the expansible bellows is located around the fuel injector inlet. In this modification the combustion chamber I5 and the exhaust nozzle outlet from it are surrounded by a cylindrical jacket I5 which is attached at the jet end to an annular disc 24 and attached at the opposite end to annular disc I9 having through it a hole I90.

forced under pressure through inlet pipe I1 and" thereby forced through chambers D, J and H and then through oriflce 21 into the motor chamber to meet the fuel injection. The heat of combustion at the constricted nozzle is conducted through the liquid at chamber D as in the case of Fig. l. The unequal expansion of jackets I5 and I5 is readily taken up by the bellows 22.

The modification shown in Fig. 3 is somewhat similar to that shownin Fig. 1, the principal difference being that instead of using a bellows 5 as in Fig. 1 there is provided a stufling box gland. This comprises the flanged member 35 fastened to the periphery of the end plate 31 and a second flanged member 33 fastened to the periphery of jacket 3|, and having its flange slidable inside the flange of member 35. Between corresponding surfaces of the two flanged members there is introduced a strip of packing 34 which is com-' pressed between the two flanged members by tightening up on bolts 35. In this way the flanged member 35, and its liquid tight packing, form partof the wall with jacket 3|, as flange 35 is also fastened to the motor plate 31.

The liquid enters through conduit 32 and passes from chamber E through holes 39 and into chamber G formed between the header 38 and plate 31 and is injected into the combustion chamber through holes 45 as in the case of Fig. 1.

A fuel and oxidizing injector arrangement is provided and constructed in the manner disclosed in my copending application, Serial No. 523,168 flled on the same date as this application, now abandoned. This comprises a fuel feed conduit 25 having located within it a helical member 45, held in a fixed position on rod 45 which is suitably fastened in a fixed position in the conduit 25.

The forward end of conduit 25 is covered by a cap 41 having centrally located in it a fuel opening 25. The exterior periphery of the cap 41 is shaped in the form of a conical frustum 49.

Around the pipe 25 there is placed a jacket 23, the forward end 55 of which is formed in a conical frustum to conform with the shape of surface 45 but leaving an annular space 21 between members 49 and 55. The jacket 23 is held in place" ened to the outside of pipe 25, and also by'a num-.

around the conduit 25 by plate 5| which is fastber of longitudinal vanes 29 extending between -pipe 25 and jacket 23.

This injector device is passed through the opening |9a of the plate I9 and snugly through wall I5 of the motor so that the nozzle end projects into the motor chamber F.

A bellows 22, is attached at one end to the outer surface of the plate I! and at the other end to the plate 5|, and if desired to the exterior of pipe 25. Suitable openings 25 are located at plate I9 so that chamber D communicates with chamber J between the bellows and pipe 25; and the arrangement is such that chambers D and J are liquid tight. Openings 2| are situated through jacket 23 at the end of the jacket remote from the holes 25 so that the fluid in jackets D and J may flow through holes 2| into jacket H.

In operation, fuel is forced under pressure my above-mentioned eopending application, Se-

rial No. 523,168 filed on the same date as this application, and then is sprayed through opening 25 into the motor chamber F. oxidizer liquid is The unequal expansion of the members 35 and 3| in this embodiment are taken up by the compressible packing 34; which being compressible, will have its dimension varied in accordance with variations of the space between the end of member 33 and the flange of member 35.

In the modification shown in Figs. 4, 5 and 6 the combustion chamber and nozzle are surrounded by a jacket for a cooling fluid-arranged to provide a fluid flow spirally from the fluid inlet at the exhaust nozzle toward the fluid outlet at the back of the combustion chamber. A spiral member 55 is formed integrally with the wall I of the chamber or may be welded to it. The outer jacket 55 abuts against the edge of the spiral so as to form a fluid-tight spiral passageway between walls I and 55. At the exhaust nozzle the area of the fluid passage becomes smaller than at the combustion chamber, and the smallest area is at the throat of the nozzle. The construction accomplishes this by the fact that at the throat the height of the convolutions of the ,spiral, for example, convolution 51 is less away from the throat than. 55 on one side and 53 on the other. A pair of solid members'55 and 5| are placed around the spiral at the nozzle to form a sort of'a doughnut, the two halves being bolted together by bolts 52 and 53. The inner curved surfaces of members 55 and 5| flt against the edges of the spiral so that the fluid passageway at the throat near convolution 51 has less area than near the more remote convolutions 55 and 59. The outer peripheries of members 55 and 5| coincide with the inner surface of jacket 55a. A number of circumferential slots 54 are placed around the members 55 and 5| and into each slot there is snapped an O ring 55 to make a fluidtight junction between the members 55 and 5| and the jackets 55 and 55a. I

The jacket 55 is separated at a position 55 which may be, for example, around an eighth of an inch, leaving the jacket portion 554 separate from the rest of the jacket 55. A rounded, annular, flexible member 51- is welded at one side to jacket portion 55 at 58, and to jacket portion 56a at 69, thereby providing the desired degree of expansion of the jacket. I

The fluid inlet is supplied from an inlet pipe '10 to the jacket at the exhaust end of the nozzle, this entrance communicating with the spiral convolution which is nearest the exhaust. The fluid under pressure travels through the spiral between the jacket and the nozzle walls and the speed of the fluid flow increases as the throat is approached owing to the constriction of the area there. Then as the fluid moves toward convolution 58 the rate of flow decreases owing to the increase of area; and adjacent the combustion chamber wall I where the area between convolutions is still greater thefluid flow decreases further. The fluid is removed from the cooling chamber through the annularly provided holes II and flows back into a chamber '12. The pressure of fluid then forces it through the injector nozzles 13 into the combustion chamber where it meets fuel forced through the fuel inlet 14 at the impingement point 15.

In the embodiment of Figs. 4 to 6 there is provided a novel and simple arrangement of the expansible memberwhich readily permits relative movement between the jacket 56 and the walls of the combustion chamber and exhaust nozzle. Moreover there is combined with the cooling chamber a conducting means in which the rate of fluid flow is made greatest at the throat of the nozzle where there is the greatest heat generated.

It will be understood that the location of the flexible member 61 might be placed differently than is shown; for example, it might be placed adjacent to the combustion chamber. In such a case the opening 66 would, of course, be located within the flexible member, Again, it would be possible to have two or more flexible members constructed with the jacket and in this case each flexible member would have its associated jacket opening.

In accordance with my invention I have provided a simple device for taking up an unequal expansion of the motor wall and of the cooling jacket wall and have provided an arrangement for effectively cooling the motor and nozzle, especially at the hottest parts.

Having thus described and illustrated my invention, I do not wish to be limited tothe details herein disclosed, otherwise than as set forth in the appended claims.

I claim:

1. In combination with a jet thrust motor comprising a cylindrical combustion chamber with a Venturi-shaped exhaust nozzle protruding from an end of the cylindrical chamber,-the nozzle having a reentrant throat and having its longitudinal axis colincar-with the longitudinal axis of the cylinder, a cylindrical jacket around the chamber and nozzle and coaxial with the axis of said chamber, said jacket being spaced from the outer wall of said chamber and nozzle to provide space for flow of cooling fluid,saidjacketcomprising two abutting sections separated from each other at a position opposite the throat of the nozzle, a flexible annular member closing the space between the abutting sections, said flexible member straddling the exterior of said space and forming a fluid-tight connection with each of the sections, an annular member within the space between the jacket and the throat of the nozzle, said annular member having a cylindrical outer surface in sliding contact with the inner jacket wall and having an inner surface shaped to conform generally with the shape of the outer wall of the nozzle, and a spiral member within the space between the annular member and the throat and forming a spiral convolution for the flow of fluid.

2. A combination according to claim 1 in which sealing ring means is provided between the cylindrical outer surface of the annular member and the inner surfaces of the jacket sections, whereby relative longitudinal motion of the jacket sections relative to the annular member may occur Without leakage of fluid past the rings.

3. A combination according toclaim 1 in which the annular member comprises va plurality of sections around the throat of the nozzle, said sections being fastened together. i

4. In combination with a jet thrust motor comprising a cylindrical combustion chamber with a Venturi-shaped exhaust nozzle protruding from an end of the cylindrical chamber, the nozzle having a reentrant throat and having its longitudinal axis colinear with the longitudinal axis of the cylinder, a cylindrical jacket around the chamber and nozzle and coaxial with the axis of said chamber, said jacket being spaced from the outer wall of said chamber and nozzle to provide space for flow of cooling fluid, said Jacket comprising two abutting sections separated from each other at a position opposite the throat of the nozzle, a flexible annular member closing the space between the abutting sections, an annular member within the space between the jacket and the throat of the nozzle, said annular member r having a cylindrical outer surface which extends across the space between the abutting jacket sections and is in sliding contact with the inner walls of said jacket sections, said annular member having an inner surface shaped to conform generally with the shape of the outer wall of the nozzle and leaving a space between the nozzle and inner surface of the annular member, and a fluid guiding member maintained within the lastmentioned space to provide a guide for fluid flow,

said guiding member serving to maintain the annular member in its position at said throat while allowing relative longitudinal movement of the jacket sections relative to the annular member.

MAURICE J. ZUCROW.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PA'I'ENTS Number Name Date 773,047 Bayles Oct. 25, 1904 871,993 Goldsborough Nov. 26, 1907 1,218,895 Porter Mar. 13, 1917 1,410,319 Junkers Mar. 21, 1922 1,726,483 Giesler Aug. 27, 1929 1,786,506 Ray Dec. 30, 1930 1,871,627 Massa Aug. 16, 1932 2,074,098 Adams Mar. 16, 1937 2,078,956 Lysholm May 4, 1937 2,408,112 iyi'uax et al Sept. 24, 1948 FOREIGN PATENTS Number Country Date 128,940 Great Britain Mar. 18, 1920 459,924 Great Britain Jan. 18, 1937 283,868 Germany Apr. 26. 1915 608,242 Germany Jan. 21, 1935 

